The kidney is normally a tremendous organizer of our small ions. It determines how much calcium to keep and how much to dump. It controls our blood’s pH by controlling which acids and bases to keep and which ones to lose. It controls sodium, potassium, calcium, carbon dioxide, water balance, and more. The kidney filters unwanted toxic biochemicals and gets rid of them in just the right amount of water necessary to maintain hydration. In failure, however, everything goes haywire. The wrong things are dumped, the wrong things are kept, toxins build up and the patient is sick. The state of toxicity that results is called “uremia” or “uremic poisoning.”

Most every animal hospital can provide diuresis: a therapy where extra fluid beyond what the patient can drink is provided thus giving the kidney its excretion medium so that it can remove toxic waste. This works well in a large number of patients but there comes a time when even with plenty of fluids, the sick kidney simply cannot get the toxins out. For most patients this is the “end of the line.” In fact, dialysis may be another choice, though it is substantially more expensive than diuresis and centers that perform dialysis for pets are still few and far between.

WHAT IS DIALYSIS?

picture courtesy of the Animal Medical Center in New York City

Dialysis is a process that can be thought of as cleansing the blood of toxins. This is done using a membrane, called a "dialyzer membrane" and a fluid called the "dialysate." The blood is separated from the dialysate by the dialyzer membrane. The dialysate fluid is formulated so that the toxins present in the blood will be attracted across the dialyzer membrane and into the dialysate fluid.

There are two types of dialysis: peritoneal dialysis and hemodialysis. When most people refer to someone needing dialysis, they mean hemodialysis. The patient is hooked up to the dialysis machine by an intravenous catheter and a pump forces the patient's blood into the machine for cleansing. The detoxified blood is returned to the patient. Peritoneal dialysis is less "high tech" and uses the patient's own abdomen as the "dialyzer membrane." The belly is filled with dialysate fluid, toxins are attracted into the fluid over several hours and the fluid (with its toxins) is drained from the belly at the end of the procedure.

HEMODIALYSIS (DESCRIPTION AND FAQ)

The intravenous catheters used in hemodialysis are very large and very long so as to support the appropriate speed of blood flow through the dialyzer. Such catheters are very difficult to place; surgery may be necessary to place them. A long term IV port under the skin may be needed if treatments are to be on going. A single catheter may be in place for months.

Dialysis catheter in place - picture courtesy ofthe Animal Medical Center in New York City

The treatment lasts 3-5 hours (sometimes longer) during which the patient must calmly sit on a table attached to equipment. Treatments typically are performed three times a week either indefinitely (as in Chronic Renal Failure) or until the kidney has healed (as in Acute Renal Failure).

There are actually numerous conditions that will benefit from this type of blood “cleansing” besides kidney failure. Electrolyte imbalances , heart failure, and many poisonings can also be treated via hemodialysis.

WHY IS THIS SO LONG IN COMING TO PETS?

Part of the problem has been that dialysis machines are generally designed for human patients. The amount of blood that goes through the human dialysis machine is too large a blood loss for a veterinary patient to withstand so smaller machines had to be built. A veterinary dialysis machine had to be designed for patients as small as a 5 or 6 lb cat. Further, a dialysis center requires specially trained staff and 24 hour care. It was difficult to get such centers financed. The procedure is still expensive and requires a dedicated owner but at least it is now an option.

HOW OFTEN IS DIALYSIS PERFORMED ON A PATIENT?

The patient who depends on dialysis to relieve the symptoms of uremia must have dialysis three times a week on the average. The pet owner must be able to bring the pet to the dialysis center with this frequency and leave the pet for the several hours needed for the treatment. Kidney transplant patients, of course, only require dialysis until they are well enough for surgery. Patients with a stone obstructing a ureter (the tube connecting the kidney and bladder) will require dialysis until stable for surgery. Patients who have lost kidney function acutely from a poisoning (usually antifreeze) or infection (usually leptospirosis) typically require a month of therapy while their kidneys heal. Other patients may require therapy indefinitely.

DOES DIALYSIS RELIABLY CONTROL UREMIC POISONING?

Not all patients respond to dialysis. How a given patient will do in part depends on what caused the kidney failure in the first place (toxin vs. infection vs. metabolic causes). Here are some statistics:

Out of 138 dogs that failed to respond to conventional therapy for kidney failure at the University of California: 40% responded to dialysis. Infectious causes (generally leptospirosis) tend to have a better prognosis. As leptospirosis has re-emerged has a common cause of canine acute kidney failure the overall response rate for dogs receiving dialysis has improved to 50%.

A study in 2003 with cats requiring hemodialysis, the response rate was 56% (the best was prognosis for those with a ureter obstruction where over 70% survived).

AT WHAT POINT IN THE TREATMENT OF KIDNEY DISEASE IS DIALYSIS RECOMMENDED?

If dialysis is being considered, it is best not to wait until conventional therapy has completely failed and the pet is on death’s door. Let your veterinarian know from the start that this is an option you are interested in so that your veterinarian can consult with the dialysis center on the best time to refer.

WHAT ARE THE COMPLICATIONS AND DISADVANTAGES?

A new world of complications (beyond those of conventionally managed kidney patients) is introduced to the renal patient on dialysis.

Malnutrition and NauseaThe toxin build-up in kidney failure causes nausea directly and appetite loss follows. Toxins further cause ulcers in the stomach and intestine which contribute even more to the loss of appetite. Once the toxins are removed, the intestine heals quickly but appetite loss may persist. Making the nutrition issue worse is the fact that dialysis patient have an increased protein requirement and an increased Calorie requirement. It is particularly important for the dialysis patient to get nutrients in one way or another. Feeding tubes or IV feeding may be necessary.

Metabolic Bone DiseaseWhen the sick kidney does not properly excrete phosphorus, calcium is mobilized in a complicated hormonal reaction (see the Calcium Phosphorus Balance page). Dialysis patients appear to be at higher risk for actual broken bones than are conventionally managed kidney patients.

Carnitine DeficiencyCarnitine is a nutrient that facilitates the transport of the body’s energy sources. Unfortunately, dialysis inherently depletes the patient of carnitine. Carnitine deficiency results in heart disease, low red blood cell count, and muscle weakness. Supplementation is often necessary for dialysis patients if dialysis is going to be regularly performed for periods longer than one month.

Taurine DeficiencyTaurine is an amino acid of animal protein origin. As is carnitine, taurine is lost in the process of dialysis with deficiency resulting in heart disease and (in cats) blindness. This amino acid must be supplemented for long term dialysis patients.

Problems with the Dialysis CatheterThe presence of the catheter may induce formation of a blood clot at the catheter tip. This can interfere with the high blood flow rates necessary for proper dialysis. When a clot occurs, a forceful flushing of the catheter may be adequate to dislodge it but if not, clot dissolving medications must be used and this becomes expensive and may lead to inability to clot.

Infection from the Dialysis CatheterAn infected dialysis catheter is bad news. The resulting blood infection can be lethal and, at best, requires months of antibiotic therapy. One should be aware of skin reddening or pus at the catheter site. The development of a fever is of great concern so the owner should become familiar with taking the pet’s temperature.

HOW MUCH DOES DIALYSIS COST?

The following information was taken from the UC Davis-San Diego Dialysis web site December 2012:

Patients requiring dialysis: Our standard dialysis estimate is $3500-$4000 for the first 2-3 treatments and $600-$700 per treatment thereafter. (This includes lab tests, dialysis catheter placement, feeding tube placement, anesthesia, oxygen, and transfusion if necessary), not including hospitalization at the Veterinary Specialty Hospital. The first three treatments will span 3-5 days. Depending on the caliber and intensity of care required by a given patient, hospitalization costs will range from $300-$1200/day. Detailed estimates are provided once a patient is assessed. Clients whose patients will be receiving dialylsis will be required to leave a deposit of between $2000-$3000 before treatment and will also be required to leave a deposit at Veterinary Specialty Hospital.

WHERE ARE THE DIALYSIS CENTERS FOR PETS?

The following are animal dialysis centers. Where possible, we have included web links which include more details about the procedure. We hope to add more centers as they open. If you are aware of an animal dialysis center not listed here please contact us so it can be included.

Continual Renal Replacement Therapy (abbreviated “CRRT”) is another form of blood filtration similar to dialysis; in fact, which procedure represents the best choice for the human patient is hotly debated in human medicine. While dialysis removes toxins built up over the previous couple of days over a 3-5 hour treatment period, CRRT involves continual removal over a 24-48 hour period which mimics the patient’s natural kidney function more closely. The idea here is to continually remove toxins until they are all gone if that is possible. Sometimes a couple of treatments are needed. This is not a regularly performed procedure like dialysis is.

The catheters are similar to the dialysis catheters but because the procedure requires being hooked to the equipment for up to two days, sedation is generally required for this entire period though this depends on the hospital.

Lower blood flow rates are used in CRRT when compared to hemodialysis which makes for fewer blood pressure issues. Also the dialysis complications that are seen over time (carnitine deficiency, high dietary Calorie requirement, catheter infection, and most of the other issues listed above) are not problems with CRRT because CRRT is done as a one time treatment). Sedation may be necessary for CRRT depending on the protocols of the facility.

Centers performing CRRT include these. (Please let us know of any others and we will add them to the list):